Summary of proposed work: (1) Studies on the effects of oocyte cytoplasm on the synthetic functions of transplanted somatic nuclei: Using appropriate genetic markers (for pigment and enzyme synthesis) we propose to carry out experiments to determine whether or not the pattern of gene activity is altered when nuclei are transferred from somatic cells to oocytes. (2) Isozyme patterns in nuclear transplant embryos: Somatic tissues are known to express different patterns of isozymes for LDH, ADH, MDH, etc. It is proposed to transplant nuclei from cells differing in these patterns into enucleated activated eggs, and to determine what patterns appear in the various parts of the resulting embryos. (3) The long range search for new mutations affecting oogenesis and embryonic or larval development will be continued. Also, analysis of the mode of action of such genes will be carried out by experimental embryological and biochemical methods.